Surgical Emergencies: Bowel Obstruction, Perforation and Ischaemia
Created | Updated Jun 10, 2012
Acute Appendicitis | Acute Pancreatitis | Acute Diverticulitis
Bowel Obstruction and Perforation | Testicular Torsion | Extradural Haematoma
Acute Limb Ischaemia | Intussusception | Ectopic Pregnancy | Pre-eclampsia and Eclampsia
Appendicitis, diverticulitis and pancreatitis represent just a few problems that may involve the bowel. The main intestinal tract can suffer from obstruction, perforation, strangulation of herniated bowel, or other lack of blood supply (mesenteric ischaemia) – all surgical emergencies and thus worth covering here. It is worth noting that various severe infections within the abdomen cause similar symptoms and signs, adding to the challenge of correctly diagnosing the cause of the problem. As a result, individuals with severe abdominal symptoms are treated as detailed in the introduction.
Most bowel-related emergencies will produce some combination of abdominal pain, nausea, vomiting, loss of appetite, constipation, abdominal tenderness, rigid abdominal wall and, in the cases such as hernias, a mass. The combination is usually enough to cause the individual to present to hospital, and will give away the fact that they are unwell. The causes of abdominal pain are many, though, and the story alone may not allow the surgeon to identify the exact diagnosis. Specific clues in the history and examination may help, as can blood tests and scans, but in some cases it is necessary to take the individual to theatre to look inside the abdomen. This may be done by passing a camera into the abdomen through a small cut, but in severely unwell individuals it is common to open the abdomen using a large midline incision.
Obstruction of the intestine accounts for perhaps one in five surgical admissions, and although the problem is usually mechanical, the cause and site of the blockage both vary. The most common causes of small bowel obstruction are strangulated hernias and adhesions between bowel loops, whereas large bowel obstruction is often a sign of bowel cancer in the older individual but can also be due to diverticular disease, volvulus of the sigmoid colon (just before the rectum), or a number of other causes. As well as simply blocking the bowel, obstruction causes leakage of vast quantities of fluid into the bowel, which in turn worsens the pressure head above the obstruction. It is possible for the bowel to perforate (see below), or to strangulate its blood supply.
Symptoms include central abdominal pain, which comes and goes as the gut contracts, abdominal distension and vomiting. Strangulation will produce constant pain with a tender abdomen, and perforation will produce a rigid 'washing board' abdomen. The initial treatment is for the individual to be Nil By Mouth, given intravenous fluids, and have a nasogastric tube inserted via the nose to allow free drainage of the stomach, which takes the pressure head off the bowel. Antibiotics are used if strangulation or perforation is suspected. A CT scan of the abdomen will help determine the cause, and guide as to what form of surgery is required to fix the underlying problem.
The intestine hangs reasonably free in the abdomen, attached to the back of the abdomen by a plane of tissue known as the mesentery. The mesentery contains the blood vessels that supply the bowel wall and muscles. It is possible for the bowel to twist on its mesentery, cutting off its blood supply while also obstructing itself – this is known as volvulus. This occurs most commonly in those with a high fibre diet and those who are prone to constipation, in particular institutionalised elderly individuals. A volvulus effectively produces the symptoms of bowel obstruction, and is usually detectable on a plain abdominal x-ray. Provided there is no suggestion that the twisted section of gut has begun to die, it is possible to treat a sigmoid volvulus (one just above the rectum) by passing a scope up into the large bowel and using a tube to decompress the bowel contents. However, in sigmoid volvulus complicated by dead bowel, and in cases of caecal volvulus (those occuring where the small bowel meets the large bowel), surgery is necessary to remove the affected bowel.
A hernia is the protrusion of abdominal contents – often bowel – out through a weakness in the lining of the abdominal cavity. If the hernia is reducible (can be pushed back in), it usually does not represent an emergency. However, if the hole through which the bowel protrudes is narrow the bowel can become stuck. If the drainage of blood from the bowel is thus cut off, the herniated bowel will become swollen and, given enough time, will die. So-called strangulated hernias are life-threatening surgical emergencies, requiring surgery to correct the hernia and remove any dead bowel found at operation.
Mesenteric ischaemia occurs when the blood supply to the bowel's supporting mesentery is cut off. This is often due to obstruction of the blood vessels with clots from the left atrium of the heart – clot formation here occurs if the heart is beating either weakly or in the wrong rhythm, as this allows blood to sit and stagnate in the atrium. The pain of mesenteric ischaemia is usually much greater than the physical signs found on examination, and is thus difficult to diagnose except when the abdominal contents are examined in theatre, revealing a dead section of bowel.
Perforation of the bowel can occur at any point from the gullet down to the rectum, though the causes differ – the gullet may rupture due to forceful vomiting, the stomach may perforate due to a deep ulcer, and the remainder of the bowel may perforate due to bowel ischaemia (lack of blood supply), appendicitis, diverticulitis, obstruction, or a number of other diseases. It may present as localised pain and tenderness if the perforation is walled off by structures within the abdomen, but otherwise will generally produce a rigid, painful abdomen and a particularly sick patient. Perforation usually necessitates a trip to theatre to remove the perforated bowel and wash out the surrounding tissues to remove as much contamination as possible.
There are a number of emergencies involving the bowel, many of which present with similar symptoms. Examination and scans are often vital in making the correct diagnosis, although sometimes it is necessary to look inside the abdomen in order to find out what is really happening.
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